1. Field of the Invention
The present invention relates to a container opening/closing device, and more particularly to a container opening/closing device with a pilfer-proof function.
2. Description of the Related Arts
Various types of container opening/closing devices with a pilfer-proof function have heretofore been known. Examples of related patents and utility models publicized in Japan are below:
Japanese Patent Publication No. 5-55386
Japanese Utility Model Publication No. 57-9240
Japanese Utility Model Laid-Open No. 56-125848
Japanese Utility Model Laid-Open No. 62-11745
These known container opening/closing devices have a structure substantially common to all of them. By way of example, one of the known devices disclosed in Japanese Patent Publication No. 5-55386 is formed as shown in FIGS. 16 and 17. In the figures, denoted by reference numeral 51 is a container mouth, and 52 is a screw cap having screws (not shown) for meshing with the mouth 51. The screw cap 52 has a skirt 53 provided with a band 55 through an easily frangible bridge 54. The band 55 is connected to a stop ring 56 through a hinge portion 57 therebetween, the stop ring 56 being bent at the hinge portion 57 to locate inside the band 55. The stop ring 56 is formed to have a thickness increasing toward its upper end. An upper bead 58 and a lower bead 59 are formed around the mouth 51.
In the container opening/closing device of the above structure, when the screw cap 52 is fitted to the mouth 51, the stop ring 56 descends and rides over the upper bead 58 while elastically deforming, and then deflects under the upper bead 58 upon restoration from its elastically deformed state. As a result, the stop ring 56 vertically engages the upper bead 58. If a pilferer, i.e., a person other than the genuine consumer, unscrews the screw cap 52 to make it open, because the band 55 cannot move up owing to the tight engagement with the upper bead 58, the bridge 54 is torn and the band 55 is moved downward, indicating that the container has been cheatingly opened.
The foregoing type of container opening/closing device with a pilfer-proof function generally, however, has common problems indicated below.
The stop ring 56 is required to have elasticity or pliability because of its need to deflect in the radial direction when it rides downwardly over the upper bead 58, but to have rigidity when the screw cap 52 is unscrewed and removed by the consumer. The reason is that when the consumer tears the bridge 54, to make the cap open, the stop ring 56, to be sufficiently pliable to be elastically deformed, has difficulty in producing a reaction force for tearing the bridge 54. Thus, the bridge 54 will not easily tear, rendering the consumer to feel embarrassed or unpleasant. It is therefore preferable for the stop ring 56 to have such a degree of rigidity that the bridge 54 is torn in a snap as soon as the screw cap 52 is unscrewed. Stated otherwise, the stop ring 56 faces the problem that it must satisfy the contradictory requirements of pliability and rigidity.
In view of the above, the stop ring 56 disclosed in the above-cited Japanese Patent Publication No. 5-55386 is formed, as shown, to have a thickness that increases toward its upper end to provide a required degree of rigidity, and decreases toward its lower end, i.e., the hinge portion 57 where the thickness is minimized, to provide a required degree of pliability.
But, because of having a thickness decreasing toward its lower end, the stop ring 56 exhibits pliability and its lower portion is elastically deformed when the consumer unscrews the cap. The bridge 54 will not tear while the stop ring 56 continues elastic deformation and is finally torn only after reaching a limit of the elastic deformation. Accordingly, the consumer feels embarrassed or unpleasant at the fact that the bridge 54 will not easily tear although the consumer applies force to the cap for making it open.
Another problem is as follows. The stop ring 56 is formed to extend obliquely downward, though not shown, when the screw cap is molded, and is thereafter inverted or folded back to extend obliquely upward. However, great force is required to invert the stop ring 56 as it can not easily be folded back.
Still another problem is that after the screw cap 52 has been unscrewed and removed, the band 55 still remains around the container mouth 51, resulting in an aesthetically worsened appearance.
With a view to solving the problems as set forth above, an object of the present invention is to provide a container opening/closing device having a component corresponding to the stop ring 56, which portion exhibits pliability so as to be able to elastically deform when a screw cap is fitted over a container, allowing that component to easily ride over a component corresponding to the upper bead 58, but exhibits rigidity when the consumer unscrews the cap to make it open, enabling a component corresponding to the bridge 54 to be immediately torn in a snap.
Another object of the present invention is to provide a container opening/closing device in which, when the component corresponding to the stop ring 56 is folded back after being formed, it can be more easily folded back than the strip ring 56 in the prior art.
Still another object of the present invention is to provide a container opening/closing device in which the component corresponding to the stop ring 56 is adaptable for large variations in size of the container mouth or the screw cap as occurred during manufacture.
Still another object of the present invention is to provide a container opening/closing device in which, after the screw cap has been unscrewed and removed, a component corresponding to the band 55 can be removed so that the container mouth has an aesthetically trim appearance.